A conventional crankshaft and con rod arrangement is commonly used to convert linear motion of a piston to rotary motion of an output shaft, or vice-versa. In these piston arrangements the piston head reciprocates within a cylinder in distorted simple harmonic motion, the distortion being due to the effective lengthening and shortening of the con rod with angular displacement. Since the piston head is only capable of moving in distorted simple harmonic motion, the performance and applications of these piston arrangements is limited. This invention relates to a piston arrangement which overcomes the limitations of a standard crankshaft and con rod type piston arrangement and its application in internal combustion engines and other systems.